Engines, such as internal combustion engines for automotive vehicles, are assembled, partly manually, in an automatic engine assembling line and ignition timing is generally set in a final stage of the engine assembling line. To set up correct ignition timing, the operator practically fires the engine to adjust ignition timing.
Because of this practical firing, it should be performed for operators' safety to cool the fired engine and remove emissions produced by the firing of the engine from the assembling site. Furthermore, because of the adjustment of ignition timing depending upon operator's perception or skill, to set correct ignition timing is a time-consuming operation and is not always performed with a high accuracy.
To avoid the above problems in setting correct ignition timing, it was thought to drive an engine with a distributor by means of a motor connected to the crankshaft of the engine under assembling and to provide a spurious firing signal for number one cylinder of the engine. The distributor is turned and adjusted in timing location with respect to the engine body in such a way as to provide the spurious firing signal at the moment a piston for the number one cylinder nears the top (ordinarily few degrees before TDC) of its compression stroke. The distributor thus adjusted in ignition timing is mechanically tightly fastened or clamped to the engine body. Such an ignition timing adjusting manner is known from Japanese Unexamined Patent Publication No. 56(1981) - 54556.
In any automatic engine assembling line, an automatic step is needed to turn the distributor with respect to the engine body for setting correct ignition timing and tightly fasten the distributor thus adjusted to the engine body. When automatically fastening or clamping the distributor to the engine body by rigidly attaching or fitting a flange of the distributor to the engine body with fastening bolts at several points, a thrust force imparted to the flange of the distributor undesirably lifts up the distributor from the engine body and tends to cause an slight turn of the distributor with respect to the engine body. This leads to the difficulty of fitting the distributor to the engine body without inducing any change of proper engagement between the distributor shaft gear and the engine crankshaft gear and, if in fact the change of proper engagement happens, results in the change of ignition timing and the engine can not fire timely, accordingly.